Method for the detection of cellular abnormalities using infrared spectroscopic imaging

Abstract

This invention teaches a method to identify cellular abnormalities which are associated with disease states. In one aspect, the invention is a method to distinguish premalignant and malignant stages of cervical cancer from normal cervical cells. The method utilizes infrared (IR) spectra of exfoliated cervical cells which are dried on an infrared transparent matrix and scanned at the frequency range from 3000-950 cm -1 . The identification of samples is based on establishing a calibration using a representative set of spectra of normal, dysplastic and malignant specimens. During the calibration process, multivariate techniques such as Principal Component Analysis (PCA) and/or Partial Least Squares (PLS) are used. PCA and PLS reduce the data based on maximum variations between the spectra, and generate clusters in a multidimensional space representing the different populations. The utilization of Mahalinobis distances, or linear regression (e.g., Principle Component Regression on the reduced data from PCA) form the basis for the discrimination. This method is simple to use and achieves statistically reliable distinction between the following groups of cervical smears: normal (individuals with no prior history of dysplasia), dysplasia and malignant samples. Further, this invention discloses a method to obtain the IR spectrum of individual cervical cells fixed on an infrared transparent matrix and to use the spectra o the individual cells in the method described above. In an additional aspect, the invention is a method for using vibrational spectroscopic imaging to distinguish between normal and diseased cells.

What is claimed is: 
     
       1. An infrared imaging method for detecting chemical differences between a cell sample and a reference cell sample comprising: (a) directing a beam of infrared light at said cell sample to produce absorption data for said cell sample;   (b) comparing said absorption data with a calibration/reference set of absorption spectra constructed by pixel-by-pixel analysis of infrared spectra acquired from at least one reference cell sample to generate comparison data;   (c) generating predicted scores for said comparison data utilizing multivariate analysis of said comparison data; and   (d) creating frequency distribution profiles from said predicted scores, whereby said detection of chemical differences is made.   
     
     
       2. A method in accordance with claim 1, wherein the cell sample comprises exfoliated cervical cells. 
     
     
       3. A method in accordance with claim 1, wherein the beam of infrared light is of a frequency selected from a group consisting of from about 3000 cm -1  to about 950 cm -1  and from about 4000 cm -1  to about 12000 cm -1 . 
     
     
       4. An infrared imaging method for distinguishing between normal, premalignant and malignant cells in a cell sample, said method comprising: (a) directing a beam of infrared light at said cell sample to produce absorption data for said cell sample;   (b) comparing said absorption data with a calibration/reference set of infrared absorption spectra constructed by pixel-by-pixel analysis of infrared absorption spectra acquired from one or more cell types selected from the group consisting of cells cytologically determined to be normal, premalignant and malignant; to generate comparison data;   (c) generating predicted scores for said comparison data utilizing multivariate analysis of said comparison data; and   (d) creating frequency distribution profiles from said predicted scores, whereby said normal, premalignant and malignant cells are distinguished.   
     
     
       5. A method in accordance with claim 4, wherein cells comprise exfoliated cervical cells.